Along with the development of the semi-conductive illuminating technology (LED), this evolutional new light source gradually enters our daily life. Using the third generation of the semi-conductive material, gallium nitride, as a semi-conductive illuminating light source, the power consumption under equivalent brightness is only one tenth comparing with normal incandescent lamp, and the service life can reach above 100,000 hours. As a new illuminating technology, LED has many advantages such as energy-saving, environment-friendliness and flexibility in application, and may be widely applied in various fields such as indication, display, decoration, backlight devices, and general illumination. Most of the currently commercialized white light LED illuminating devices employ blue-light LED chips in coordination with fluorescent powders which emit yellow, green or orange lights under excitation of blue lights. This type of fluorescent powders has relatively high luminescent efficiency, and the preparation method thereof is well-established. However, the light source devices produced by this method have the following disadvantages: (1) the epoxy resins used for encapsulation are liable to deteriorate and would become yellow under the illumination of blue, violet or ultra-violet lights, leading to decrease in the service life of the devices; (2) the process is complex and the cost is relatively high; and (3) the light decay rates of the fluorescent powders and the chips are different, resulting in that the color coordinates are instable and that the white light is liable to drift.
In comparison with powder materials, glass ceramics, which achieve luminescence under excitation of violet or ultraviolet lights, have significant advantages: (1) good light transmission; (2) exceptional chemical and thermal stability; (3) simple preparation process and low cost; (4) liability to be made into bulk and various shapes; and (5) possibility to substitute epoxy resins. Due to these characteristics, glass ceramics capable of achieving high performance luminescence are very suitable as the luminescent media materials in the LED lamination field. Accordingly, it is in great need to find suitable substrates and rare earth ions for glass ceramics which are suitable for emitting white light under the excitation of blue or ultra-violet lights. However, as the lattice structure of glass is compact, the solid solubility of rare earth ions in the lattice of glass is relatively low. In addition, commonly used silicate glasses have relatively high phonon energy, resulting in high probability of non-radiative recombination of the doped rare earth ions. This significantly reduces the probability of radiative recombination of the rare earth ions, resulting in low luminescent intensity, or even no luminescence, of rare earth ions in glass.